The preparation and reactions of carbonyl-stabilised ammonium ylides

Base catalysed rearrangements involving ylide intermediates. Part 15. The mechanism of the Stevens [1,2] rearrangement

“…( 6) relative to tetramethylsilane as an internal reference. A and B ) (6).--.The ylide (4a) was prepared as a monohydrate, m.p. 75-82 "C (lit.…”

“…75-82 "C, which could be stored at 0 "C for one year without noticeable decomposition. Thermal rearrangement of the ylide (4a) in chloroform at 60 "C gave the [1,2] rearrangement product (5a) as the major product together with 1,2-diphenylethane, the diastereoisomeric diamines (6), and N,N-dimethylbenzylamine. A similar set of products was obtained under a variety of reaction conditions in yields that depended upon the conditions used (see Table 6, Experimental section) and these products accounted for 1 9 5 % of the total reaction product.…”

“…A similar set of products was obtained under a variety of reaction conditions in yields that depended upon the conditions used (see Table 6, Experimental section) and these products accounted for 1 9 5 % of the total reaction product. The diamine (6) was synthesised, as the single diastereoisomer A, m.p. 156-158 "C, by the reaction of (E)-1,2-dibenzoylethylene with dimethylamine in the presence of iodine; a low yield of the vinylogous amide (7) was also obtained from this reaction.…”

“…The reaction was therefore investigated by treating the ammohiurn salt (3b) with base. In methanol at 55 "C, using sodium methoxide as the base, the salt (3b) gave the [1,2] rearrangement product (5b) as the major product as a mixture of both diastereoisomers (1 : 1 ratio), together with small quantities of both diastereoisomers of 2,3-diphenylbutane (1 : 1 ratio), and diastereoisomers A and B of the diamine (6) (3 : 1 ratio). The rearrangement of the salt (3b) in water at 0 "C, using sodium hydroxide as the base, gave the [1,2] rearrangement product (5b) as a mixture of diastereoisomers (5 : 4 ratio) and small quantities of 1-phenylethanol and both diastereoisomers of the acyloin (8) (5 : 3 ratio).…”

Cyclopenta[c]pyrans

“…In a later work [44], dealing with base‐catalyzed rearrangements involving ylide intermediates, 39 was reported as one of the thermolysis products of anhydro[decyldimethyl(phenacyl)ammonium hydroxide].…”